Ejection condition determination method, image forming method, and image forming apparatus

ABSTRACT

An ejection condition determination method in an image forming apparatus includes: selecting two or more kinds of ejection conditions regarding other recording elements than a specified recording element among plural recording elements; acquiring drawing data representing two or more drawing patterns having different density distributions, the drawing data being acquired by respectively forming same drawing patterns using the selected two or more kinds of ejection conditions in a specified non-ejection state; performing a filter processing corresponding to human visual characteristics on the acquired drawing data so as to obtain visual correction drawing data; and determining the ejection conditions for compensating for a density variation of the image due to the specified non-ejection state based upon evaluation results which are obtained by respectively evaluating two or more drawing patterns represented by the visual correction drawing data and having been subjected to the filter processing according to a predetermined evaluation condition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ejection condition determinationmethod of determining an ejection condition of droplets by relativelymoving a recording medium only once with respect to a recording headincluding a plurality of recording elements which eject the droplets ina transport direction crossing an arrangement direction of the pluralityof recording elements, so as to form an image formed by a plurality ofdots on the recording medium, and an image forming method and an imageforming apparatus using the ejection condition determination method.

2. Description of the Related Art

In recent years, with the rapid progress of an ink jet technique, colorand large size printing in which high speed and high image quality arecompatible has been realized by an ink jet recording type image formingapparatus. In this recording type, droplets of a plurality of kinds ofinks (for example, CMYK inks) are ejected onto a recording medium so asto form a plurality of dots, thereby obtaining a printed matter. Thiskind of apparatus is used for, particularly, a wide field in applicationto signs and display, and is also applicable to printing of, forexample, a storefront point of purchase (POP), wall poster outdooradvertising, a signboard, and the like.

In addition, in this recording type, a single pass type of using arecording head (hereinafter, referred to as a line head) including aplurality of nozzles arranged in a predetermined direction has attractedspecial attention. This is because an image can be formed by moving arecording medium or a line head only once in a transport directioncrossing the predetermined direction, and various specifications (highspeed, low power consumption, and high image quality) required inapplication to signs and display can be all compatible.

Meanwhile, it is most preferable that ejection states of all the nozzlesincluded in the line head be favorable at all times in order to stablyobtain high quality printed matters. However, it is realistically verydifficult to secure and maintain the above-described ejection states inall line heads in terms of productivity including processing accuracy,costs, and the like. Therefore, various image correction techniques forpositively suppressing deterioration in image quality have been proposedon the premise that there may be a defective nozzle in the line head.

JP2011-201121A (Abstract, and FIGS. 3 and 17) has proposed a method andan apparatus in which a correction coefficient for non-ejectioncorrection is determined in view of the fact that patterns of landinginterference occurrence are different depending on relative positionalrelationships between respective nozzles. JP2011-201121A also describesa drawing example of a test chart which is a set of patches formed withvarious ejection conditions.

JP2006-076086A (claim 2 and FIG. 12) and JP2007-160748A (claim 1,paragraph [0069], and the like) have proposed a method and an apparatusin which density reduction due to non-ejection from a defective nozzleis compensated for using N (where N is an integer of 2 or more) nozzlesaround the defective nozzle. Particularly, JP2006-076086A (claim 2 andFIG. 12) specifically discloses addition and subtraction of a correctionamount becoming smaller as the distance from the defective nozzleincreases being repeated alternately for each pixel.

SUMMARY OF THE INVENTION

However, in a case where the correction disclosed in JP2011-201121A,JP2006-076086A, and JP2007-160748A is performed in practice, there arevarious kinds and values of controllable parameters (hereinafter,referred to as control parameters) such as the number of nozzles usedfor the correction, an ejection amount of droplets, the number of colorplates, and grayscale levels. In other words, there are cases wherecorrection accuracy of image density is improved, whereas a large numberof operation steps are required to select an optimal ejection condition.Therefore, as disclosed in paragraph [0006] of JP2007-160748A, aconfiguration is considered in which an image density of a test patternis optically read using a scanning device, and each control parameter isautomatically determined from the obtained digital data.

However, according to the result of earnest research of the presentinventors, it was found that even if each control parameter isdetermined using the above-described method, the control parameter tendsnot to necessarily conform to a user's sense (checking result throughvisual observation). Particularly, in relation to a correction amountexemplified in JP2006-076086A, there are cases where density unevenness(relatively thin stripe unevenness due to non-ejection of droplets ordeviation of landed positions) in a high spatial frequency band can bereduced, but rather density unevenness in a low spatial frequency bandcaused by a nozzle of which a control parameter is adjusted becomesobvious, and thus it is difficult to perform an operation of determiningan optimal control parameter.

The present invention has been made in view of the above-describedproblems, and an object thereof is to provide an ejection conditiondetermination method capable of considerably reducing the number ofoperation steps and determining an ejection condition conforming to auser's sense, and an image forming method and an image forming apparatususing the ejection condition determination method.

According to an aspect of the present invention, there is provided anejection condition determination method in an image forming apparatusconfigured to relatively move a recording medium once with respect to arecording head including a plurality of recording elements configured toeject droplets in a transport direction crossing an arrangementdirection of the plurality of recording elements, so as to form an imageformed by a plurality of dots on the recording medium. The methodincludes selecting two or more kinds of ejection conditions regardingother recording elements than a specified recording element among theplurality of recording elements; acquiring drawing data representing twoor more drawing patterns having different density distributions, thedrawing data being acquired by respectively forming same drawingpatterns using the selected two or more kinds of ejection conditions ina specified non-ejection state in which there is no ejection of thedroplets from the specified recording element; performing a filterprocessing corresponding to human visual characteristics on the acquireddrawing data so as to obtain visual correction drawing data; anddetermining the ejection conditions for compensating for a densityvariation of the image due to the specified non-ejection state basedupon evaluation results which are obtained by respectively evaluatingtwo or more drawing patterns represented by the visual correctiondrawing data and having been subjected to the filter processingaccording to a predetermined evaluation condition.

As above, since a filter processing corresponding to human visualcharacteristics is performed on drawing data representing two or moredrawing patterns which are different in density distribution, it ispossible to obtain drawing data representing a drawing form closer to amanner viewed by a user, that is, visual correction drawing data. Inaddition, since an ejection condition for compensating for a densityvariation of an image caused by a specified non-ejection state isdetermined based on an evaluation result obtained by respectivelyevaluating the two or more drawing patterns having been subjected to thefilter processing according to predetermined evaluation conditions, itis possible to automatically determine an optimal ejection conditionwhile comparing and evaluating two or more kinds of ejection conditions,respectively. Therefore, it is possible to considerably reduce thenumber of operation steps and to determine an ejection conditionconforming to a user's sense.

In addition, in the selecting of the two or more kinds of ejectionconditions, the two or more kinds of ejection conditions may be selectedin which dot forming conditions for forming the dots are different forat least one of the recording elements adjacent to the specifiedrecording element.

Further, the dot forming condition may include at least one of anejection amount of the droplets, an ejection speed of the droplets, anda dot density.

In addition, the selecting of the two or more kinds of ejectionconditions, the acquiring of the drawing data, the performing of thefilter processing, and the determining of the ejection conditions may besequentially repeatedly performed, so as to sequentially determine thedot forming condition for the recording elements and to fix the ejectionconditions.

Further, the dot forming conditions for the recording elements locatedoutside the specified recording element in a predetermined direction maybe sequentially determined so as to fix the ejection conditions.

In addition, the same drawing pattern may be a flat pattern having auniform color.

In addition, the ejection condition determination method may furtherinclude forming the two or more drawing patterns as the image on therecording medium by using the image forming apparatus, and, in theacquiring of the drawing data, the two or more formed drawing patternsmay be read using a scanning device which adopted to optically read theimage, so as to acquire the drawing data.

Further, in the acquiring of the drawing data, the two or more drawingpatterns may be read in a reading direction which is determinedaccording to optical transfer characteristics of the scanning device, soas to acquire the drawing data.

In addition, the ejection condition determination method may furtherinclude inputting image forming information regarding the image formingapparatus, and, in the acquiring of the drawing data, digital datasimulating difference in density distribution may be created using theinput image forming information, so as to acquire the drawing data.

According to another aspect of the present invention, there is providedan image forming method including forming the image by controllingejection of the recording head in the specified non-ejection state basedupon the ejection conditions determined using any one of theabove-described methods.

According to still another aspect of the present invention, there isprovided an image forming apparatus including the recording head ofwhich ejection is controlled in the specified non-ejection state basedupon the ejection conditions determined using any one of theabove-described methods, so as to form the image.

According to the ejection condition determination method, the imageforming method and the image forming apparatus using the ejectioncondition determination method related to the present invention, since afilter processing corresponding to human visual characteristics isperformed on drawing data presenting two or more drawing patterns whichare different in density distribution, it is possible to obtain drawingdata representing a drawing form closer to a manner viewed by a user,that is, visual correction drawing data. In addition, since an ejectioncondition for compensating for a density variation of an image caused bya specified non-ejection state is determined based on an evaluationresult obtained by respectively evaluating the two or more drawingpatterns having been subjected to the filter processing according topredetermined evaluation conditions, it is possible to automaticallydetermine an optimal ejection condition while comparing and evaluatingtwo or more kinds of ejection conditions, respectively. Therefore, it ispossible to considerably reduce the number of operation steps and todetermine an ejection condition conforming to a user's sense.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating a main configurationfor realizing an ejection condition determination method according to afirst embodiment.

FIG. 2 is a transparent plan view illustrating a configuration exampleof the recording head shown in FIG. 1.

FIG. 3 is a schematic cross-sectional view taken along the line in FIG.2.

FIG. 4 is a schematic explanatory diagram illustrating a correspondencerelationship between an arrangement example of a plurality of nozzlesand an ejection order on a sheet.

FIG. 5 is a flowchart provided for description of an operation of theejection condition determination portion of FIG. 1.

FIG. 6 is a schematic plan view illustrating an example of a defectivenozzle specifying chart.

FIG. 7A is a schematic plan view illustrating an example of an imageadjusting chart, and FIG. 7B is an enlarged view of a flat pattern.

FIG. 8 is a graph of a Dooley-Shaw function (observation distance 300mm).

FIGS. 9A and 9B are schematic explanatory diagrams regarding anevaluation method of a flat pattern.

FIGS. 10A to 10D are schematic explanatory diagrams illustrating adetermination process of a dot gain control parameter.

FIG. 11 is a graph illustrating a determination example of a dot gaincontrol parameter of the nearest adjacent nozzle and the second nearestadjacent nozzle.

FIGS. 12A-12D are the schematic explanatory diagram regarding an effectof non-ejection correction.

FIG. 13 is a schematic block diagram illustrating a main configurationfor realizing an ejection condition determination method according to asecond embodiment.

FIG. 14 is a specific flowchart regarding an acquisition method ofdrawing data in step S4A of FIG. 5.

FIG. 15 is a cross-sectional side view illustrating a configuration ofan image forming apparatus.

FIG. 16 is an electrical block diagram illustrating a systemconfiguration of the image forming apparatus shown in FIG. 15.

FIGS. 17A and 17B are transparent plan views illustrating otherconfiguration examples of the recording head shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an ejection condition determination method according to thepresent invention will be described in detail using preferredembodiments in a relationship with an image forming method and an imageforming apparatus which performs the method. In this specification, toform an image is referred to as “printing” in some cases.

Configuration According to First Embodiment

Schematic Block Diagram

FIG. 1 is a schematic block diagram illustrating a main configurationfor realizing an ejection condition determination method according to afirst embodiment.

An ejection condition determination portion 10, which is a core of theembodiment of the present invention, determines an ejection condition ofdroplets 14 in an image forming apparatus 100 (refer to FIGS. 15 and 16)which forms a color image or a monochrome image formed by a plurality ofdots on a sheet 12 (recording medium). In addition, the ejectioncondition determination portion 10 is capable of sending and receiving avariety of data to and from a scanning device 16 and a data storageportion 18.

The ejection condition determination portion 10 includes a drawing dataacquisition section 22, a filter processing section 24, and a patternevaluation section 26. The drawing data acquisition section 22 acquiresdrawing data representing an image adjusting chart 20 (refer to FIGS. 1and 7A) described later. The filter processing section 24 performs afilter processing corresponding to human visual characteristics on thedrawing data. The pattern evaluation section 26 evaluates a flat pattern70 (refer to FIG. 7B) according to a predetermined evaluation condition.

The scanning device 16 optically reads an image on a printed matterincluding the image adjusting chart 20 so as to generate digital data.The scanning device 16 may be a flat scanner provided for reading areflected original document, or may be a film scanner provided forreading a transmitted original document.

The data storage portion 18 stores a variety of data required to performthis determination method. In this drawing example, the data storageportion stores chart image data 28, a plurality of kinds of visualcharacteristic data items 30, a plurality of kinds of evaluationcondition data items 32, and ejection condition data 34.

A head driver 38 is a driving circuit which controls driving of fourrecording heads 40 based on a control signal provided for forming animage so as to eject the droplets 14 at appropriate timing. Here, asingle pass type is shown in which the sheet 12 is transported only oncein the arrow Y direction crossing (perpendicular to) the arrow Xdirection in a state of fixing each recording head 40 which is a linehead extending in the arrow X direction.

Configuration of Recording Head 40

FIG. 2 is a transparent plan view illustrating a structure example ofthe recording head 40 shown in FIG. 1. FIG. 3 is a schematiccross-sectional view taken along the line of FIG. 2.

As shown in FIG. 2, the recording head 40 includes a plurality of inkchamber units 42 (recording elements) which are arranged in a zigzagmatrix. Each ink chamber unit 42 includes a nozzle 44, a pressurechamber 45, and a supply port 46. In the pressure chamber 45 which has asubstantially rectangular planar shape, an outflow port to the nozzle 44side is provided at one corner of both corners disposed diagonally, andan inflow port (the supply port 46) from a common channel 48 is providedat the other corner thereof.

As shown in FIG. 3, each pressure chamber 45 communicates with thecommon channel 48 via the supply port 46. In addition, the commonchannel 48 communicates with an ink tank (not shown) which is a supplysource of an ink (color material). Thus, the ink supplied from the inktank is distributed and supplied to each pressure chamber 45 via thecommon channel 48.

One surface (corresponding to an upper surface in the example of FIG. 3)of the pressure chamber 45 is constituted by a pressing plate 50, andthe pressing plate 50 is also used as a common electrode. Apiezoelectric element 52 which is an actuator giving pressure to thepressing plate 50 so as to be deformed is joined onto the pressing plate50. In addition, an individual electrode 54 is formed on the uppersurface of the piezoelectric element 52.

When a driving voltage is applied between two electrodes, that is, thepressing plate 50 which is a common electrode and the individualelectrode 54, the piezoelectric element 52 interposed between the twoelectrodes is deformed. This physical deformation causes a volume of thepressure chamber 45 to vary, and thus the ink is pushed outward from thenozzle 44 and is ejected as the droplets 14 (refer to FIG. 1). Inaddition, after the droplets 14 are ejected, an ink refills the pressurechamber 45 via the supply port 46 from the common channel 48 when thedisplacement of the piezoelectric element 52 returns to an originalstate.

Referring to FIG. 2 again, an arrangement feature of the nozzles 44 willbe described. In FIG. 2, a longitudinal direction and a transversedirection of the recording head 40 are respectively defined as an arrowX direction and an arrow Y direction. In this case, a transportdirection (refer to FIG. 1) of the sheet 12 is perpendicular to thearrow X direction and is parallel to the arrow Y direction.

The respective nozzles 44 in the L1-th line are disposed at the sameinterval with a predetermined gap (corresponding to four unit lengths)in the arrow X direction. The respective nozzles in the L2-th to L4-thlines are also disposed in the same manner as in the L1-th line.Hereinafter, the arrow X direction is referred to as an “arrangementdirection” of the nozzles 44 (the ink chamber units 42) in some cases.

Each nozzle 44 in the L2-th line is disposed at a position which isshifted by one unit length to the left in the arrow X direction from theposition of each nozzle 44 in the L1-th line. Each nozzle 44 in theL3-th line is disposed at a position which is shifted by one unit lengthto the left in the arrow X direction from the position of each nozzle 44in the L2-th line. Each nozzle 44 in the L4-th line is disposed at aposition which is shifted by one unit length to the left in the arrow Xdirection from the position of each nozzle 44 in the L3-th line.Therefore, an actual gap (projected nozzle pitch) between the nozzles 44projected so as to be arranged in the longitudinal direction of therecording head 40 becomes small for high density.

FIG. 4 is a schematic explanatory diagram illustrating a correspondencerelationship between a first arrangement example of a plurality ofnozzles 44 included in the recording head 40 and an ejection order ontothe sheet 12. For convenience of description, a case of using twentynozzles 44 will be described as an example.

Each cell in the rectangular lattice shown in FIG. 4 indicates a regionof one pixel in a formed image. The blank cell indicates an imageposition where the droplets 14 (refer to FIG. 1) are not ejected(landed) yet at each ejection time point (t). In addition, the arabicnumeral shown in the cell corresponds to a time point (ejection timepoints t=1 to 7) when the droplets 14 are ejected at the image positionthereof.

For example, a plurality of dots are sequentially formed by the droplets14 ejected between the ejection time points t=1 and 4, so as to generatea first image line. In addition, a plurality of dots are sequentiallyformed by the droplets 14 ejected between the ejection time points t=4and 7, so as to generate a fourth image line. In other words, dots aresequentially formed at a plurality of (four in FIG. 4) timings so as togenerate (complete) each image line.

Operation of Ejection Condition Determination Portion 10

Next, an operation of the ejection condition determination portion 10shown in FIG. 1 will be described in detail with appropriate referenceto a flowchart of FIG. 5 and other drawings.

In step S1, at least one nozzle 44 (a so-called defective nozzle) inwhich an ejection operation of the droplets 14 is not favorable isspecified among a plurality of nozzles 44 included in the recording head40.

FIG. 6 is a schematic plan view illustrating an example of a nozzlespecifying chart 60. As shown in FIG. 6, a plurality of line images 62parallel to the arrow Y direction are formed on the nozzle specifyingchart 60. In order to clarify a relationship between each nozzle 44 andeach line image 62, a method of forming the nozzle specifying chart 60will be described below.

First, the droplets 14 are ejected from the respective nozzles 44 atintervals of three among the nozzles 44 belonging to the L1-th line, soas to form a line image group 64 of one row. Next, the droplets 14 areejected from other nozzles 44, for example, respective nozzles 44adjacent rightward to the initially used nozzles 44, so as to form aline image group 66 of one row. When this operation is sequentiallyperformed four times, the line images 62 formed by only the nozzles 44belonging to the L1-th line are disposed in the number corresponding tothe number of the nozzles 44 belonging to the L1-th line on the sheet12.

As above, it is possible to check an ejection operation of each nozzle44 on the nozzle specifying chart 60 by respectively forming the lineimages 62 using the respective nozzles 44 of the L2-th to L4-th lines inthe same manner as in the L1-th line. For example, in a case where noline image 62 is formed, a nozzle 44 corresponding to the line image 62is specified not to eject the droplets 14. In addition, in a case wherethe line image 62 is relatively tilted, a nozzle 44 corresponding to theline image 62 is specified to cause curved ejection (i.e., abnormalmeniscus).

The nozzle specifying chart 60 may be checked through visualobservation, and then identification information of a specified nozzle44 d may be input through a manual operation. Alternatively, the nozzlespecifying chart 60 may be read using an image reading mechanismembedded in the image forming apparatus 100 (refer to FIG. 15) whileprinting the nozzle specifying chart, and then a specified nozzle 44 dmay be automatically detected thereby identification information of theautomatically detected nozzle may be input.

In addition, in subsequent steps S2 to S10, an ejection condition of theother nozzles 44 is determined so as to perform non-ejection correctionof the nozzle 44 (hereinafter, a specified nozzle 44 d; refer to FIG. 4)specified in step S1. Here, the “non-ejection correction” indicates animage correction technique of stopping an ejection operation of thespecified nozzle 44 d in which an ejection operation of the droplets 14is not normal and compensating for a density variation (mainly, adensity reduction) of an image due to this stopping.

In step S2, two or more kinds of ejection conditions regarding the othernozzles 44 than the specified nozzle 44 d are selected. Here, theejection condition indicates a set of combinations of kinds and valuesof control parameters regarding ejection control of each nozzle 44. Theejection condition includes, for example, position information of thenozzle 44, identification information (identification number, the numberof continuous nozzles, or the like) of the specified nozzle 44 d, dotforming conditions, grayscale level info nation (halftone %), colorinformation (the kind of color plate, or the like), and combinationsthereof. The position information of the nozzle 44 may include, forexample, a relative position to the specified nozzle 44 d, a pitch ofthe nozzles 44, a positional relationship in the recording head 40 (forexample, attributes of the L1-th to L4-th lines shown in FIG. 2), andthe like. The dot forming conditions are various conditions for formingdots through ejection of the droplets 14, and include, for example, atleast one of an ejection amount of the droplets 14, an ejection ratethereof, and a dot density (so-called recording density).

In this embodiment, ejection conditions in which dot forming conditionsfor nozzles in a vicinity of the specified nozzle 44 d, for example, atleast one of (for example, four) nozzles 44 adjacent thereto aredifferent are selected, respectively.

In step S3, the image adjusting chart 20 on which the respectiveejection conditions selected in step S2 are reflected is printed usingthe image forming apparatus 100 (refer to FIG. 15). Specifically, thehead driver 38 acquires the chart image data 28 stored in the datastorage portion 18, and then controls driving of each recording head 40so as to obtain the image adjusting chart 20.

As shown in FIG. 7A, a plurality of flat patterns 70 (drawing patterns)having uniform colors (for example, the substantially same lightreflectance, luminance and density), nine patterns in the example ofFIG. 7A are drawn in each image adjusting chart 20. Each flat pattern 70may be obtained by forming the same drawing pattern (here, an image withthe same pixel value) by using each ejection condition determined instep S2 in a state in which the droplets 14 are not ejected from thespecified nozzle 44 d (hereinafter, a specified non-ejection state). Forthis reason, the respective flat patterns 70 macroscopically have theapproximately same density but microscopically have different densitydistributions.

In addition, in the present specification, a two-dimensionaldistribution of a color of an image is referred to as a “densitydistribution”, but an index for indicating a color of an image is notlimited to an “optical density”. In other words, all indexes (forexample, light reflectance, luminance, luminosity, and the like)indicating a color of an image may be employed as a two-dimensionaldistribution.

In the example of FIG. 7A, a dot gain of nozzles 44 (hereinafter, thenearest adjacent nozzles 44 n; refer to FIG. 4) closest to the specifiednozzle 44 d from the lower side to the upper side increases in the sameimage adjusting chart 20. In addition, a dot gain of nozzles(hereinafter, the second nearest adjacent nozzles 44 m; refer to FIG. 4)which are the second closest from left to right increases.

As shown in FIG. 7B, the flat pattern 70 includes a non-ejection region72 which is an image region corresponding to a position of the specifiednozzle 44 d, adjustment target regions 74 which are image regionscorresponding to positions of the nearest adjacent nozzles 44 n and thesecond nearest adjacent nozzles 44 m, and non-adjustment target regions76 which are image regions corresponding to positions of the othernozzles 44. Here, the “image region corresponding to a position of thenozzle 44” mainly indicates an image region in which a color is formedon the recording medium 12 through ejection of the droplets 14 from thecorresponding nozzle 44. Particularly, the non-adjustment target region76 is used as a reference image so as to clarify adjustment targets ofthe image in the non-ejection region 72 and the adjustment target region74.

In addition, the specified non-ejection state may be realized by settinga control signal value corresponding to an ejection position of thespecified nozzle 44 d to 0, or the specified non-ejection state may berealized by directly giving a non-ejection command to the head driver38.

Further, a form of a drawing pattern forming the image adjusting chart20 may employ a geometric pattern such as a stripe, a circle, a dot, ora mark other than the flat pattern. Particularly, it is more preferableto use the flat pattern 70 in which an image quality difference is mosteasily detected.

Further, in the example of FIG. 7A, for easy discrimination, therespective flat patterns 70 are disposed spaced apart from each otherwith a specific gap in the image adjusting chart 20. A form of the flatpattern is not limited thereto, and, for example, the flat pattern maybe an integrated pattern without a space. In this case, it is normallydifficult to differentiate ejection condition differences from eachother on an image, and thus a variety of information with which aposition of each drawing pattern is specified is preferably held inadvance.

In step S4, the drawing data acquisition section 22 acquires drawingdata representing the image adjusting chart 20 formed in step S3. Beforethe acquisition, the scanning device 16 optically reads the image of theimage adjusting chart 20 (including the nine flat patterns 70) so as tobe supplied to the ejection condition determination portion 10 side.Further, the drawing data acquisition section 22 acquires the obtaineddigital data (device-dependent data such as RGB, and optical physicalquantities such as reflectance and transmittance) as drawing datawithout modification, or converts the digital data intodevice-independent data such as L*a*b.

Here, an image reading direction may be determined based on an opticaltransfer function (OTF) of the scanning device 16. Specifically, an axisdirection with higher OTF of two axis directions of an image readingregion is made to match a horizontal direction (the arrangementdirection of the nozzles 44; the X direction) of the image adjustingchart 20 shown in FIG. 7A, and thus it is possible to suppress influenceof sharpness decrease caused by the scanning device 16.

In step S5, the ejection condition determination portion 10 selects onedata item from each of a plurality of visual characteristic data items30 and a plurality of evaluation condition data items 32. For example,the data item may be selected depending on the kind of image adjustingchart 20 or may be selected by receiving an input operation by a user.

In step S6, the filter processing section 24 performs a filterprocessing in which one visual characteristic data item 30 selected instep S5 has acted on the drawing data acquired in step S4. Here, the“filter processing” indicates an image process of modulating a spatialfrequency component (spectral intensity) of an image.

FIG. 8 is a graph of a Dooley-Shaw function (observation distance 300mm). This function is a kind of visual transfer function (VTF) and is arepresentative function which models human standard visual responsecharacteristics. Specifically, the function corresponds to the squarevalue of contrast ratio characteristics of luminance. The transverseaxis of the graph expresses a spatial frequency (the unit: cycle/mm),and the longitudinal axis expresses a value (the unit is dimensionless)of the VTF.

The filter processing section 24 performs inverse Fourier transform (forexample, IFFT) on the square root of the VTF shown in FIG. 8 so as tocalculate a mask on the real space corresponding to the VTF in advance.Then, the filter processing section 24 performs a convolution operationon the drawing data acquired from the drawing data acquisition section22 by using a mask corresponding to a resolution thereof. Thus, it ispossible to obtain visual correction drawing data.

In addition, a function shape of visual characteristics is not limitedthereto, and various visual characteristics derived from mathematicalmodels, test data, or the like may be employed. Further, an observationdistance may not only correspond to 300 mm but be also variously changeddepending on observation aspects or evaluation references of an image,or the like.

In addition, in order to appropriately reflect a correction effectthrough the above-described filter processing, a pixel value of drawingdata is preferably converted into an (preferably, linear) amount withhigh correlation with an amount of light reflected by or transmittedthrough an image. As an example thereof, RGB values, tristimulus values(XYZ), light reflectance in a case of a reflection original document,light transmittance in a case of a transmission original document, orthe like may be used.

In step S7, the pattern evaluation section 26 evaluates two or more flatpatterns 70 which have been subjected to the filter processing accordingto the evaluation condition data items 32 selected in step S5.Hereinafter, a specific example of the evaluation will be described indetail.

FIGS. 9A and 9B are schematic explanatory diagrams regarding anevaluation method of the flat pattern 70. A profile 78 common to both ofFIGS. 9A and 9B indicates a microscopic density distribution from oneend E1 to the other end E2 (refer to FIGS. 7A and 7B) of the flatpattern 70. The profile 78 has two peaks indicating maximum points of animage density and three peaks indicating minimum points of the imagedensity. In addition, an ideal line 79 indicated by the broken line inFIGS. 9A and 9B corresponds to an average density (an ideal density) ata position which is sufficiently spaced apart from the specified nozzle44 d.

The pattern evaluation section 26 may evaluate each flat pattern 70 byplacing importance on an extent in which stripe unevenness occurs. Asshown in FIG. 9A, a difference P1 between the maximum value and an idealdensity may be an evaluation value, or a difference P2 between themaximum value and the minimum value of the image density may be anevaluation value. In this case, the smaller the difference P1 or P2, thehigher an evaluation, and, the larger the difference P1 or P2, the loweran evaluation.

The pattern evaluation section 26 may evaluate each flat pattern 70 byplacing importance on macroscopic reproducibility of an image density.As shown in FIG. 9B, when, with respect to the ideal lines 79, the areasof two regions on the upper side are respectively indicated by Sp1 andSp2, and the areas of three regions on the lower side are respectivelySm1, Sm2, and Sm3, the integral St=|(Sp1+Sp2)−(Sm1+Sm2+Sm3)| may be anevaluation value. In this case, the smaller the integral St, the higheran evaluation, and, the larger the integral St, the lower an evaluation.

In addition, a method of calculating an evaluation value is not limitedthereto, and various methods or indexes appropriate for quantificationof density unevenness of an evaluation target, and combinations thereof,may be used. As an example of an evaluation method, in addition to theabove-described statistical process, well-known image processing methodsincluding a feature amount extraction process may be performed.Specifically, a low-pass filter may be applied in a case of evaluatingstrip unevenness having a component of a low spatial frequency band, anda high-pass filter or an edge detection filter may be applied in a caseof evaluating stripe unevenness having a component of a high spatialfrequency band. In addition, this process may be performed separatelyfrom/together with the above-described filter processing (step S6).

Further, from the viewpoint of an averaged error, a longitudinal axis ofthe profile 78 is preferably converted into an (preferably, linear)amount with high correlation with an amount of light reflected by ortransmitted through an image. As an example thereof, RGB values,tristimulus values (XYZ), light reflectance in a case of a reflectionoriginal document, light transmittance in a case of a transmissionoriginal document, or the like may be used.

In step S8, the ejection condition determination portion 10discriminates whether or not to finish this evaluation based on theevaluation result obtained in step S7. The ejection conditiondetermination portion 10 discriminates whether or not there is at leastone flat pattern 70 which satisfies an evaluation reference capable ofrealizing image quality of an allowable level. If it is discriminatedthat there is no flat pattern, the flow returns to step S2, and adifferent ejection condition different from in the previous time isselected again, and steps S2 to S8 are sequentially repeatedlyperformed. On the other hand, if it is discriminated that there is atleast one flat pattern, the flow proceeds to the next step (S9). Inaddition, the flow may proceed to the next step (S9) without performingthe discrimination process.

In step S9, the ejection condition determination portion 10 determinesan optimal ejection condition on the basis of the evaluation resultobtained in step S7. For example, the ejection condition determinationportion 10 may determine an ejection condition having the highestevaluation result among a plurality of ejection conditions as an optimalejection condition. Alternatively, the ejection condition determinationportion 10 may estimate an evaluation value in an intermediate ejectioncondition from a relationship between a plurality of ejection conditionsand evaluation values, and may determine an ejection condition which isexpected to obtain the highest evaluation result as an optimal ejectioncondition.

In step S10, the optimal ejection condition determined in step S9 is setand is preserved. Specifically, the ejection condition determinationportion 10 sends data regarding the optimal ejection condition so as tobe stored in the data storage portion 18.

In this way, an operation of the ejection condition determinationportion 10 is completed. An optimal ejection condition in which aplurality of control parameters are variously combined may be determinedby repeatedly performing the flowchart of FIG. 5 as necessary.

For example, there are cases where it is difficult to perform anoperation of determining an optimal control parameter when an image isadjusted using nozzles 44 around the specified nozzle 44 d, the nearestadjacent nozzles 44 n, the second nearest adjacent nozzles 44 m, and theother nozzles 44. Specifically, even if density unevenness (a relativelythin stripe unevenness due to non-ejection or landing position deviationof the droplets 14) of a high spatial frequency band is reduced as aresult of image adjustment, density unevenness of a low spatialfrequency band caused by the nozzle 44 for which a control parameter isadjusted may become more obvious. Similarly, as a result of suppressingdensity unevenness of a low spatial frequency band, density unevennessof a high spatial frequency band may become more obvious.

Therefore, a method may be employed in which a dot forming condition foreach nozzle 44 is sequentially determined through sequential repetitionof steps S2 to S9 of FIG. 5, and then a final ejection condition isfixed. Particularly, an ejection condition is preferably sequentiallydetermined for the nozzles 44 located on the outside in a predetermineddirection (for example, an arrangement direction) from the specifiednozzle 44 d.

FIGS. 10A to 10D are schematic explanatory diagrams illustrating adetermination process of a dot gain control parameter. FIG. 10A showsthe nearest adjacent nozzles 44 n, the second nearest adjacent nozzles44 m, and the third nearest adjacent nozzles 44 l in an order of beingclose to the specified nozzle 44 d. For convenience of description, astate is shown in which seven nozzles 44 are disposed in a line. Inaddition, FIGS. 10B to 10D are the same as FIG. 10A.

The circle with X indicates the specified nozzle 44 d. In addition, thenormal circle indicates a nozzle 44 of which a dot gain controlparameter is a default value and a dot gain is not adjusted. Further,the hatched circle indicates a nozzle 44 of which a value of a dot gaincontrol parameter is variously changed. Furthermore, the filled circleindicates a nozzle 44 of which a value of a dot gain control parameteris fixed.

In the first image adjustment, two or more kinds of ejection conditionsin which values of the dot gain control parameters of the two nearestadjacent nozzles 44 n and 44 n are variously changed are selected, andone kind of ejection condition thereof is determined (refer to FIG.10B). Here, the dot gain control parameters of the two second nearestadjacent nozzles 44 m and 44 m and the two third nearest adjacentnozzles 44 l and 44 l are respectively set to default values.

In the second image adjustment, after a value of the dot gain controlparameter of each of the nearest adjacent nozzles 44 n and 44 n isfixed, two or more kinds of ejection conditions in which values of thedot gain control parameters of the second nearest adjacent nozzles 44 nand 44 n are variously changed are selected, and one kind of ejectioncondition is determined from the conditions (refer to FIG. 10C).

Next, if it is determined that image quality is in an allowable level, avalue of the dot gain control parameter of each of the second nearestadjacent nozzles 44 m and 44 m is fixed (refer to FIG. 10D). As such,the number of nozzles 44 which is a control parameter is reduced so asto narrow options, thereby improving efficiency of the adjustmentoperation. In addition, a dot forming condition is sequentiallydetermined in an order in which an adjustment amount (a variation amountfrom a reference value) of a dot gain is large, and thus an imageadjustment performance is rapidly improved.

On the other hand, conversely to the above description, if sequentialdetermination is performed from the outside of the specified nozzle 44 dto the inside in a predetermined direction (for example, an arrangementdirection), this is not efficient from the viewpoint of image adjustmentsince a dot forming condition is determined in an order in which anadjustment amount of a dot gain is small.

In addition, although values of control parameters are determinedindependently from each other in the above-described example, values ofcontrol parameters may be determined under any constraints. An exampleof the constraint may include an upper limit of a total amount of ink tobe used, an operation range of a control parameter, or the like.

FIG. 11 is a graph illustrating an example of determining controlparameters of the nearest adjacent nozzles 44 n and the second nearestadjacent nozzles 44 m, and shows an example (look-up table) of a dataformat in the ejection condition data 34 (refer to FIG. 1). Thetransverse axis of this graph expresses a dot recording ratio (unit: %),and the longitudinal axis thereof expresses a control parameter. Inaddition, the control parameter has a standard value of 1, is a variablewhich is proportional to a dot gain (or a dot density), and iscorrelated with an ejection amount or ejection speed (or halftone %) ofthe droplets 14.

As understood from FIG. 11, a control parameter for compensating for adensity variation of an image due to a specified non-ejection state isset. In other words, dot gains of the nearest adjacent nozzles 44 n arerelatively increased so as to increase a density around the ejectionposition of the specified nozzle 44 d. In addition, dot gains of thesecond nearest adjacent nozzles 44 m are relatively reduced so as toreduce densities around the ejection positions of the nearest adjacentnozzles 44 n.

Effects According to this Ejection Condition Determination Method.

Returning to FIG. 1, the ejection condition data 34 which is stored inthe data storage portion 18 in advance is referred to when an image isformed on the sheet 12 using the recording head 40. In other words, thehead driver 38 multiplies a dot gain corresponding to each nozzle 44 byan input control signal, and controls ejection of each recording head 40on the basis of an obtained signal value. Thus, it is possible torealize non-ejection correction on any image.

As shown in FIGS. 12A-12D, in a case where curved ejection occurs in thespecified nozzle 44 d, visible white stripe unevenness and black stripeunevenness are generated on an image 90. In contrast, it is possible toobtain a favorable image 91 on which stripe unevenness is not viewed byselecting an appropriate ejection condition. In addition, dot gains ofthe second nearest adjacent nozzles 44 m are relatively reduced so as toachieve a so-called decimation effect and to thereby improve robustnessto disparity between landing positions and landing interference of thedroplets 14 ejected from the nearest adjacent nozzles 44 n. Accordingly,it is possible to obtain favorable images 92 and 93 in which stripeunevenness is not viewed.

As described above, since a filter processing corresponding to humanvisual characteristics (the visual characteristic data items 30) isperformed on drawing data representing two or more flat patterns 70which are different in density distribution, it is possible to obtaindrawing data representing a drawing form closer to a manner viewed by auser, that is, visual correction drawing data. In addition, since anejection condition (the ejection condition data 34) for compensating fora density variation of an image caused by a specified non-ejection stateis determined based on an evaluation result obtained by respectivelyevaluating the two or more flat patterns 70 having been subjected to thefilter processing according to predetermined evaluation conditions (theevaluation condition data items 32), it is possible to automaticallydetermine an optimal ejection condition while comparing and evaluatingtwo or more kinds of ejection conditions, respectively. Therefore, it ispossible to considerably reduce the number of operation steps and todetermine an ejection condition conforming to a user's sense.

Configuration According to Second Embodiment

FIG. 13 is a schematic block diagram illustrating a main configurationfor realizing an ejection condition determination method according to asecond embodiment. In addition, the same constituent elements as in thefirst embodiment have the same reference numerals and descriptionthereof will be omitted.

The second embodiment has the substantially same configuration as thefirst embodiment shown in FIG. 1 but is different in that an imagecreation device 80 is provided instead of the scanning device 16. Theimage creation device 80 includes an information input portion 82 whichinputs a variety of information (hereinafter, image forming information)for forming an image in an image forming apparatus 100 (refer to FIG.15), and a drawing data creation portion 84 which creates digital datasimulating the image adjusting chart 20 (refer to FIG. 7A) by using theimage forming information input by the information input portion 82.

Operation of Ejection Condition Determination Portion 10

Next, an operation of the ejection condition determination portion 10shown in FIG. 13 will be described. This operation is basically the sameas in the flowchart of FIG. 5, but step S4A is executed instead of stepS4 for reading an image of the image adjusting chart 20. Hereinafter, adetailed description thereof will be made with appropriate reference tothe flowchart of FIG. 14 and other drawings.

In step S4A-1, the information input portion 82 inputs image forminginformation provided for creating an image. Here, the image forminginformation includes a variety of information regarding the imageforming apparatus 100 including an output resolution, a variety ofinformation regarding ink or the recording medium 12, and a variety ofinformation regarding a drawing specification of the image adjustingchart 20 including the above-described ejection condition.

In step S4A-2, the drawing data creation portion 84 creates digital datasimulating the image adjusting chart 20 (refer to FIG. 7A) by using theimage forming information input in step S4A-1. The drawing dataacquisition section 22 acquires the obtained digital data as drawingdata without modification, or converts the digital data intodevice-independent data such as L*a*b.

In step S4A-3, the drawing data acquisition section 22 acquires thedigital data created in step S4A-2. In the present embodiment, the imagecreation device 80 and the ejection condition determination portion 10are shown as different constituent elements, but each function of theinformation input portion 82 and the drawing data creation portion 84may be executed by the ejection condition determination portion 10.

In the above-described way, the drawing data acquisition section 22acquires the drawing data simulating the image adjusting chart 20 (stepS4A).

In addition, unlike in the first embodiment, since a drawingspecification (for example, a definition of a pixel value and a positionin the unit of a pixel) in the drawing data is known, it is possible toefficiently perform a filter processing (step S6 of FIG. 5) orevaluation (step S7 of FIG. 5) of each drawing pattern by using thisinformation. In addition, as shown in FIGS. 10A to 10D, an ejectioncondition of the droplets 14 may be sequentially determined.

Effects According to this Ejection Condition Determination Method.

As above, image forming information regarding the image formingapparatus 100 (refer to FIG. 15) is input, and digital data simulating adifference in density distribution on the image adjusting chart 20 iscreated using the image forming information. Therefore, it is possibleto easily determine an ejection condition conforming to a user's sensewithout actually forming the image adjusting chart 20. Particularly,since consumable materials such as ink or the recording medium 12 arenot necessary, costs are reduced.

Configuration of Image Forming Apparatus 100

Successively, a description will be made of an ejection conditiondetermination method related to the above-described first and secondembodiments and the image forming apparatus 100 capable of realizing animage forming method using this method. FIG. 15 is a cross-sectionalside view illustrating a configuration of the image forming apparatus100.

The image forming apparatus 100 is provided with a paper feeding andtransport portion 114 which feeds and transports the sheet 12 on theupstream side in the transport direction of the sheet 12 (in the exampleof FIG. 15, flat paper). A treatment liquid application portion 116which applies a treatment liquid on a recording surface (hereinafter,referred to as an image forming surface) of the sheet 12, an imageforming portion 118 which forms an image by attaching the droplets 14(refer to FIG. 1) of ink onto the image forming surface, an ink dryingportion 120 which dries ink of a treatment liquid layer formed on thesheet 12, an image fixing portion 122 which fixes the image of thetreatment liquid layer to the sheet 12, and a discharge portion 124which discharges the sheet 12 to which the image is fixed, are providedon the downstream side of the paper feeding and transport portion 114 inthe transport direction of the sheet 12.

The paper feeding and transport portion 114 includes a stacking section126 which is provided so as to stack the sheets 12, a paper feedingsection 128 which feeds the sheets 12 stacked on the stacking section126 one by one, and a transport section 130 which transports the sheet12 fed by the paper feeding section 128 to the treatment liquidapplication portion 116.

The treatment liquid application portion 116 includes a treatment liquidapplication drum 132 which is rotatably provided, a treatment liquidapplication device 134 which applies a treatment liquid on the imageforming surface of the sheet 12, and a treatment liquid drying device136 which dries the treatment liquid. Thus, a thin treatment liquidlayer is applied on the image forming surface of the sheet 12.

A first intermediate transport drum 138 is rotatably disposed betweenthe treatment liquid application portion 116 and the image formingportion 118. The first intermediate transport drum 138 is rotated in astate in which the sheet 12 is held on the surface of the firstintermediate transport drum 138, and thus the sheet 12 supplied from thetreatment liquid application portion 116 side is transported to theimage forming portion 118 side.

The image forming portion 118 includes an image forming drum 140(transport section) which is rotatably provided, and a head unit 142which ejects the droplets 14 onto the sheet 12 transported by the imageforming drum 140. The head unit 142 includes the recording heads 40(refer to FIG. 1) of at least Y (yellow), M (magenta), C (cyan), and K(black) which are primary colors. In addition, the respective recordingheads 40 are arranged in the circumferential direction of the imageforming drum 140. Therefore, images of the respective colors aresequentially formed on the treatment liquid layer applied on the imageforming surface of the sheet 12. Further, the treatment liquid has aneffect of condensing color materials (pigments) and latex particlesdispersed in a solvent of the ink, and thus can prevent the colormaterials from flowing on the sheet 12.

A second intermediate transport drum 146 which is rotatably provided isdisposed between the image forming portion 118 and the ink dryingportion 120. The second intermediate transport drum 146 is rotated in astate in which the sheet 12 is held on the surface of the secondintermediate transport drum 146, and thus the sheet 12 supplied from theimage forming portion 118 side is transported to the ink drying portion120 side.

The ink drying portion 120 includes an ink drying drum 148 which isrotatably provided, and a plurality of hot air nozzles 150 and aplurality of infrared heaters (heaters 152) which dry the treatmentliquid layer of the sheet 12. Thus, the solvent of the ink remaining inthe treatment liquid layer of the sheet 12 is dried.

A third intermediate transport drum 154 which is rotatably provided isdisposed between the ink drying portion 120 and the image fixing portion122. The third intermediate transport drum 154 is rotated in a state inwhich the sheet 12 is held on the surface of the third intermediatetransport drum 154, and thus the sheet 12 supplied from the ink dryingportion 120 side is transported to the image fixing portion 122 side.

The image fixing portion 122 includes an image fixing drum 156 which isrotatably provided, a heating roller 158 which is disposed so as to beclose to the surface of the image fixing drum 156, and a fixing roller160 which is disposed in a state of coming into pressing contact withthe surface of the image fixing drum 156. Therefore, the latex particlescondensed in the treatment liquid layer are heated and pressed and arethus fixed onto the sheet 12 as an image.

The sheet 12 to which the image of the image forming surface is fixedthrough the above-described respective steps is transported to thedischarge portion 124 side provided on the downstream side of the imagefixing portion 122 through rotation of the image fixing drum 156.

Description of Control System of Image Forming Apparatus 100

FIG. 16 is a block diagram illustrating a system configuration of theimage forming apparatus 100 shown in FIG. 15. The image formingapparatus 100 includes not only the data storage portion 18, the headdriver 38 (refer to FIG. 1 with regard to both of the two), the headunit 142, and the heater 152 (refer to FIG. 15 with regard to both ofthe two), but also a communication interface 162, a system controller164, an image memory 166, a ROM 168, a motor driver 170, a motor 172, aheater driver 174, a printing control portion 176, an image buffermemory 180, and a ROM 182.

The communication interface 162 is an interface portion with a hostapparatus 190, and is used for a user to instruct the image formingapparatus 100 to form an image or the like. The communication interface162 may employ a serial interface such as a universal serial bus (USB),IEEE1394, Ethernet (registered trademark), or a wireless network, or aparallel interface such as Centronics. A buffer memory (not shown) forspeeding up communication may be mounted in this portion.

An image signal sent from the host apparatus 190 is received by theimage forming apparatus 100 via the communication interface 162 and istemporarily stored in the image memory 166. The image memory 166 isstorage means for storing an image signal input via the communicationinterface 162, and reads and writes information via the systemcontroller 164. The image memory 166 is not limited to a memory formedby semiconductor elements, and may use a magnetic medium such as a harddisk.

The system controller 164 includes a central processing unit (CPU) andperipheral circuits, functions as a control device controlling theoverall image forming apparatus 100 according to a predeterminedprogram, and functions as an operation device including the ejectioncondition determination portion 10 and performing various operations. Inother words, the system controller 164 controls the respective portionssuch as the communication interface 162, the image memory 166, the motordriver 170, and the heater driver 174. In addition, the systemcontroller 164 performs communication control with the host apparatus190, reading and writing control of the image memory 166 and the ROM168, and the like. Further, the system controller 164 generates controlsignals for controlling the motor 172 and the heaters 152 of the sheettransport system. Furthermore, an image signal stored in the imagememory 166 as well as the control signal is transmitted to the printingcontrol portion 176.

The ROM 168 stores programs executed by the CPU of the system controller164 and a variety of data necessary for control. The image memory 166 isused as a temporary storage region of an image signal and is used as adevelopment region of a program and an operation work region of the CPU.

The motor driver 170 is a driver (driving circuit) which drives themotor 172 of the sheet transport system in response to an instructionfrom the system controller 164. The heater driver 174 is a driver whichdrives the heaters 152 in response to an instruction from the systemcontroller 164.

On the other hand, the printing control portion 176 includes a CPU andperipheral circuits, and performs processes such as various processingsfor generating an ejection control signal from an image signal of theimage memory 166 and correction and supplies the generated ink ejectiondata (control signal) to the head driver 38 so as to control ejectiondriving of the head unit 142 under the control of the system controller164.

The printing control portion 176 includes the image buffer memory 180,and an image signal or data such as a parameter is temporarily stored inthe image buffer memory 180 when the printing control portion 176processes the image signal.

The printing control portion 176 is connected to the ROM 182 whichstores programs executed by the CPU of the printing control portion 176and a variety of data necessary for control. The ROM 182 may be readonly storage means, but preferably uses rewritable storage means such asan EEPROM in a case where a variety of data is updated as necessary.

An image processing section 184 generates dot disposition data for eachink color from an input image signal. In other words, a halftone processis performed on the input image signal so as to determine a dot formingposition (ink ejection timing). The halftone process may employ anordered dither method, an error diffusion method, a density patternmethod, a random dot method, and the like. In addition, in a case wherea dot density is changed so as to realize non-ejection correction, theimage processing section 184 may perform the halftone process afteradjusting a part of the input image signal by referring to the ejectioncondition data 34 (refer to FIG. 1) stored in the data storage portion18.

In addition, in the example of FIG. 16, the ejection conditiondetermination portion 10 and the image processing section 184 arerespectively included in the system controller 164 and the printingcontrol portion 176. For example, the ejection condition determinationportion 10 and/or the image processing section 184 may be configuredseparately from the system controller 164 or the printing controlportion 176.

In addition, the printing control portion 176 has an ink ejection datageneration function of generating ink ejection data (a control signal ofthe actuators corresponding to the nozzles 44 of the recording head 40)and a driving waveform generation function on the basis of the dotdisposition data generated by the image processing section 184.

The ink ejection data generated using the ink ejection data generationfunction is sent to the head driver 38 so as to control an ink ejectionoperation of the head unit 142. During the control, the above-describednon-ejection correction is performed by referring to the ejectioncondition data 34 (refer to FIG. 1) stored in the data storage portion18.

The driving waveform generation function is a function of generating adriving signal waveform for driving the actuator corresponding to eachnozzle 44 of the recording head 40. A signal (driving waveform)generated using the driving waveform generation function is supplied tothe head driver 38.

Other Configurations of Recording Head 40

A configuration of the recording head 40 is not limited to the exampleof FIGS. 2 to 4. For example, a shape of the pressure chamber 45 is notlimited to this example, and various forms may be employed in which aplanar shape is a tetragonal shape (a diamond shape, a rectangularshape, or the like), a pentagonal shape, a hexagonal shape, otherpolygonal shapes, a circular shape, an elliptical shape, and the like.

In addition, instead of the configuration of FIG. 2, as shown in FIG.17A, short head modules 40 a in which a plurality of nozzles 44 arearranged in a two-dimensional manner may be arranged in a zigzag shapeand be connected to each other so as to form a long line head. As shownin FIG. 17B, a form may be employed in which head modules 40 b arearranged in a line and are connected to each other.

Further, an ejection mechanism of the droplets 14 by the recording head40 may employ various types. In addition to a type (refer to FIG. 3) ofejecting the droplets 14 through deformation of an actuator formed by apiezoelectric element and the like, a thermal jet type may be employedin which a heating element such as a heater heats ink so as to generatebubbles and the droplets 14 are ejected by a pressure thereof.

In addition, the present invention is not limited to the above-describedembodiment, and can be freely modified in the scope without departingfrom the spirit of the invention.

Although, in the above-described embodiment, the graphic art (printing)usage is exemplified, an applicable scope of the present invention isnot limited thereto. The present invention is applicable to variousimage forming apparatuses capable of forming an image pattern, such as,for example, a wire drawing apparatus of an electronic circuit board, amanufacturing device of various devices, a resist printing apparatususing a resin liquid as a functional liquid (corresponding to “ink”) forejection, and a micro-structure forming apparatus.

In addition, although, in the above-described embodiment, only the sheet12 is transported through rotation of the image forming drum 140, atleast one of the head unit 142 and the sheet 12 may be transported. Thepresent invention is applicable to a configuration in which both of thehead unit and the sheet 12 are relatively moved.

What is claimed is:
 1. An ejection condition determination method in animage forming apparatus configured to relatively move a recording mediumonce with respect to a recording head including a plurality of recordingelements configured to eject droplets in a transport direction crossingan arrangement direction of the plurality of recording elements, so asto form an image formed by a plurality of dots on the recording medium,the method comprising: selecting two or more kinds of ejectionconditions regarding other recording elements than a specified recordingelement among the plurality of recording elements; acquiring drawingdata representing two or more drawing patterns having different densitydistributions, the drawing data being acquired by respectively formingsame drawing patterns using the selected two or more kinds of ejectionconditions in a specified non-ejection state in which there is noejection of the droplets from the specified recording element;performing a filter processing for modulating a spatial frequencycomponent with a visual transfer function on the acquired drawing dataso as to obtain visual correction drawing data; and determining theejection conditions for compensating for a density variation of theimage due to the specified non-ejection state based upon evaluationresults which are obtained by respectively evaluating two or moredrawing patterns represented by the visual correction drawing data andhaving been subjected to the filter processing according to apredetermined evaluation condition.
 2. The ejection conditiondetermination method according to claim 1, wherein, in the selecting ofthe two or more kinds of ejection conditions, the two or more kinds ofejection conditions are selected in which dot forming conditions forforming the dots are different for at least one of the recordingelements adjacent to the specified recording element.
 3. The ejectioncondition determination method according to claim 2, wherein the dotforming condition includes at least one of an ejection amount of thedroplets, an ejection speed of the droplets, and a dot density.
 4. Theejection condition determination method according to claim 3, whereinthe selecting of the two or more kinds of ejection conditions, theacquiring of the drawing data, the performing of the filter processing,and the determining of the ejection conditions are sequentially andrepeatedly performed, so as to sequentially determine the dot formingcondition for the recording elements and to fix the ejection conditions.5. The ejection condition determination method according to claim 4,wherein the dot forming conditions for the recording elements locatedoutside the specified recording element in a predetermined direction aresequentially determined so as to fix the ejection conditions.
 6. Theejection condition determination method according to claim 2, whereinthe selecting of the two or more kinds of ejection conditions, theacquiring of the drawing data, the performing of the filter processing,and the determining of the ejection conditions are sequentially andrepeatedly performed, so as to sequentially determine the dot formingcondition for the recording elements and to fix the ejection conditions.7. The ejection condition determination method according to claim 6,wherein the dot forming conditions for the recording elements locatedoutside the specified recording element in a predetermined direction aresequentially determined so as to fix the ejection conditions.
 8. Theejection condition determination method according to claim 2, whereinthe same drawing pattern comprises a flat pattern having a uniformcolor.
 9. The ejection condition determination method according to claim2, further comprising: forming the two or more drawing patterns as theimage on the recording medium by using the image forming apparatus,wherein, in the acquiring of the drawing data, the two or more formeddrawing patterns are read using a scanning device adopted to opticallyread the image, so as to acquire the drawing data.
 10. The ejectioncondition determination method according to claim 9, wherein, in theacquiring of the drawing data, the two or more drawing patterns are readin a reading direction which is determined according to optical transfercharacteristics of the scanning device, so as to acquire the drawingdata.
 11. The ejection condition determination method according claim 2,further comprising: inputting image forming information regarding theimage forming apparatus, wherein, in the acquiring of the drawing data,digital data simulating difference in density distribution is createdusing the input image forming information, so as to acquire the drawingdata.
 12. An image forming method comprising: forming the image bycontrolling ejection of the recording head in the specified non-ejectionstate based upon the ejection conditions determined using the methodaccording to claim
 2. 13. An image forming apparatus comprising therecording head of which ejection is controlled in the specifiednon-ejection state based upon the ejection conditions determined usingthe method according to claim 2, so as to form the image.
 14. Theejection condition determination method according to claim 1, whereinthe same drawing pattern comprises a flat pattern having a uniformcolor.
 15. The ejection condition determination method according toclaim 1, further comprising: forming the two or more drawing patterns asthe image on the recording medium by using the image forming apparatus,wherein, in the acquiring of the drawing data, the two or more formeddrawing patterns are read using a scanning device adopted to opticallyread the image, so as to acquire the drawing data.
 16. The ejectioncondition determination method according to claim 15, wherein, in theacquiring of the drawing data, the two or more drawing patterns are readin a reading direction which is determined according to optical transfercharacteristics of the scanning device, so as to acquire the drawingdata.
 17. The ejection condition determination method according claim 1,further comprising: inputting image forming information regarding theimage forming apparatus, wherein, in the acquiring of the drawing data,digital data simulating difference in density distribution is createdusing the input image forming information, so as to acquire the drawingdata.
 18. An image forming method comprising: forming the image bycontrolling ejection of the recording head in the specified non-ejectionstate based upon the ejection conditions determined using the methodaccording to claim
 1. 19. An image forming apparatus comprising therecording head of which ejection is controlled in the specifiednon-ejection state based upon the ejection conditions determined usingthe method according to claim 1, so as to form the image.